What is Multiple Sclerosis (MS)?

What is Multiple Sclerosis (MS)?

Multiple sclerosis (MS) is a chronic neurological disease of the optic nerves, brain, and spinal cord, which comprise the central nervous system.  MS causes the immune system to mistakenly attack the body’s nerve cells and damage their protective, insulating layer called the myelin sheath. The nerves then deteriorate, which prevents the brain from communicating correctly with the rest of the body.

The intensity of symptoms experienced by patients with MS varies widely. Some people experience loss of vision or the ability to walk or talk. Others experience numbness or tingling sensations, while some people experience long periods with no new symptoms. There is no cure for MS, but specific treatments can reduce the frequency and severity of new symptoms , while others help manage existing symptoms.

MS affects about one million Americans and is more common in women than men. MS typically appears in young adults between the ages of 20 and 40, though it can manifest from childhood and well into older age.

Types of Multiple Sclerosis (MS)


The types of MS are based on the disease’s course as it progresses. The specific type can be determined depending on whether or not there are relapses (periods in which symptoms emerge, worsen, then stop partially or completely) or gradual worsening of disability.

All types of MS can also be classified as active or not active. “Active” describes a condition in which relapses are experienced, or new areas of damage to the central nervous system (called lesions) can be seen on an MRI scan. The condition is considered “not active” if no lesions or relapses exist. “Progression” describes gradual worsening in the absence of relapse, whereas “worsening” encompasses disability accrual whether from incomplete relapse recovery or gradual progression without relapse.

Relapsing-remitting multiple sclerosis

Relapsing-remitting MS involves cycles of relapse and remission. Symptoms usually persist for days or weeks and then disappear or lessen for weeks, months, or years (with or without treatment). In some cases, symptoms may worsen with each relapse and increase the person’s level of disability. Relapsing-Remitting MS is the most common type of MS, accounting for about 85% of diagnoses.

Primary progressive multiple sclerosis

About 10-15% of MS diagnoses are primary progressive MS. It occurs when the condition gradually worsens and causes increased levels of disability over time without periods of remission. People with this type experience worsening symptoms, including stiffness or heaviness of limbs, and increased difficulty in movement. Though possible, it’s uncommon for people with this type to have relapses.

Secondary progressive multiple sclerosis

Secondary progressive MS begins as relapsing-remitting MS. It occurs when relapsing-remitting MS advances to the point where there are no longer periods of remission. In this type, symptoms gradually worsen over time, and people often experience increased levels of disability without being able to identify a specific episode as the cause. Though there are no periods of remission, in some cases, people still experience relapses when the condition progresses to this type. 

Early diagnosis and treatment  are crucial in limiting the damage MS can cause to the central nervous system. Clinically isolated syndrome (CIS) describes a person’s first episode of neurological symptoms that are experienced for at least 24 hours. Symptoms may cause dizziness, numbness, difficulty walking, bladder-control issues, or vision problems. In some cases, CIS can be the first indicator of MS, and doctors can perform tests to determine a person’s risk of developing MS after CIS.

Signs & Symptoms of Multiple Sclerosis (MS)


Multiple sclerosis can affect almost any part of the central nervous system, which means symptoms can vary widely from patient to patient. Common symptoms of MS include changes to the senses such as:

  • Vision problems, including double vision, blurred vision, or loss of vision (optic neuritis)
  • Weakness
  • Imbalance
  • Vertigo
  • Numbness
  • Pain or tingling sensations
  • Fatigue and cognitive impairment are common symptoms and the leading reasons that individuals with MS leave the workforce

People with MS may have symptoms that affect motor function and control, including coordination, walking, or balance problems. Some people also experience tremors, slurring, speaking difficulty, bladder issues (such as urgent or frequent urination), or limb stiffness.

MS symptoms in men

Men are more likely to be diagnosed with primary progressive MS, though the exact reason for this is still being investigated. Men can experience symptoms of sexual dysfunction due to MS, and tend to have more neurodegeneration (brain atrophy and loss of nerve functionality) than women. Men’s cognitive symptoms are typically more intense than those in women. This may be due to higher levels of estrogen in women, a hormone that helps protect and support the nervous system.

MS symptoms in women

Women with MS tend to have more inflammatory lesions than men when an MRI scan is performed. Men tend to show more atrophy including spinal cord atrophy. Women with MS while pregnant may notice that their symptoms lessen during pregnancy but then rise again about three months after childbirth. Women may also notice that their MS symptoms worsen during and after menopause. Sex hormone shifts during menopause may be linked to these changes in disease features.

What Causes Multiple Sclerosis (MS)?


The exact causes of multiple sclerosis are unclear, though it is considered an autoimmune disease in which the immune system attacks the central nervous system.

Information travels to and from the central nervous system through impulses. Nerve cells have an insulating outer layer called the myelin sheath to support the transmission of these impulses to and from the brain so that we can properly process and respond to information. In people with MS, the immune system attacks this myelin sheath, disrupting proper communication between the brain and the rest of the body.

Medical professionals and researchers are studying possible causes that may trigger this immune system response. Potential triggers include infections, viruses, and environmental and genetic factors.

Risk Factors for Multiple Sclerosis (MS)

Risk Factors

Certain genetic, environmental, and behavioral factors can increase the likelihood of developing multiple sclerosis. Risk factors for multiple sclerosis include:

  • Age - MS can manifest at any age but typically affects people between the ages of 20 and 40. It is extremely rare to see an onset before the age of 11 or after the age of 60.
  • Sex - MS affects more than twice as many women as men
  • Family history - People who have a parent or sibling with MS have a higher likelihood of developing the condition
  • Certain infections - Studies show that MS is linked to specific viral infections, such as measles, human herpes virus 6 (HHV-6), and Epstein-Barr (EBV). EBV is the strongest known risk factor for MS.
  • Race - MS affects more white people than people of African, Asian, or Native American descent.
  • Low levels of Vitamin D – Low levels of vitamin D have been linked to an increased risk of MS
  • Climate - MS is more common in parts of the world with temperate climates, such as the northern United States, Canada, New Zealand, Europe, and southern parts of Australia
  • Certain autoimmune diseases - People with autoimmune diseases such as thyroid disease, psoriasis, type 1 diabetes, or inflammatory bowel disease have a higher chance of developing MS
  • Smoking - After the initial episode of MS symptoms, people who smoke are more likely than non-smokers to have a second episode that signifies relapsing-remitting MS
  • Obesity - Childhood and adolescent obesity, particularly in girls, increases the risk of developing MS later in life

Other environmental exposures, such as pesticides and high salt diets, are being evaluated as potential risk factors for MS.

Get Care

Trust NewYork-Presbyterian for Personalized Multiple Sclerosis (MS) Care

Medical experts at NewYork-Presbyterian understand the symptoms of MS and know how MS can affect your life and the lives of your family members. A healthcare team of specialists, including neurologists, physical therapists, social workers, psychologists, and other medical professionals, are here to help at every step.

We will communicate with you and your family to provide the support you need, creating a customized treatment plan to maximize your function, improve your quality of life, and increase your independence. Schedule an appointment with one of our medical experts to learn more about treatment for MS and the care services provided by NewYork-Presbyterian.